1. Field of the Invention
The present invention relates to a ratchet mechanism that permits a rotary power tool to be used in a manual ratchet mode for alternatively tightening or loosening a screw.
2. Description of the Prior Art
DE 4128651 A1 describes an electric screwdriver with a ratchet and pawl arrangement to permit manual screwdriving when the motor is inoperative. The tool operates in four distinct modes: forward and reverse power drill/driving modes plus forward and reverse manual ratchet modes. One of the four modes is conveniently selected via a rotating switch. In both of the manual ratchet modes, the motor is electrically decoupled via movement of electrical contacts that are mechanically coupled to the rotating switch. A problem with this design is that if the motor is inadvertently activated while the tool is in a ratchet mode, the motor could jam and possibly be damaged. It would be useful to have a rotary power tool with the manual ratchet functionality but without the associated risks to the motor.